Exopolysaccharide Biosynthesis by Lactobacillus helveticus ATCC15807

TORINO, MARÍA INÉS; MOZZI, FERNANDA; FONT DE VALDEZ, GRACIELA

APPLIED MICROBIOLOGY AND BIOTECHNOLOGY

Springer

Lugar: Berlin Heidelberg; Año: 2005 vol. 68 p. 259 - 265

0175-7598

The exopolysaccharide (EPS) production and the activities of the enzymes involved in the sugar nucleotides biosynthesis in Lactobacillus helveticus ATCC 15807 under controlled pH conditions were investigated. Batch fermentations using lactose as energy source showed higher EPS synthesis by L. helveticus ATCC 15807 at pH 4.5 respect to pH 6.2, the enzyme a-phosphoglucomutase (a-PGM) being correlated with both total and specific EPS production. When glucose was used as carbon source instead of lactose, the lower EPS synthesis obtained was linked to a decrease of the a-PGM and galactose 1-phosphate-uridyltransferase (GalT) activities; the reduction of this latter one being more pronounced. Higher EPS production by L. helveticus ATCC 15807 at the acidic constant pH of 4.5 requires both high a-PGM and GalT activities. These enzymes are needed to synthesise UDP-glucose and UDP-galactose for supplying the corresponding monomers for the EPS biosynthesis. Although the differences observed in the EPS production by this strain regarding the energy source (lactose or glucose), the monomeric composition of the polymers produced was independent of the carbohydrate used. The obtained results contribute to a better understanding of the physiological factors that affect EPS biosynthesis by lactobacillus; approach which would help to the correct handling of the fermentation parameters within the fermented dairy industry.